The vascular system of the human is subject to blockage due to plaque within the arteries. Partial and even complete blockage of arteries by the formation of an atherosclerotic plaque is a well known and frequent medical problem. Frequently, such blockage occurs in the coronary arties. Such blockages may be treated using atherectomy devices, which mechanically remove the plaque; hot or cold lasers, which vaporize the plaque; stents, which hold the artery open; and other devices and procedures which have the objective of allowing increased blood flow-through the artery.
The most common of such procedures is the percutaneous transluminal coronary angioplasty (PTCA) procedure—more commonly referred to as balloon angioplasty. In this procedure, a catheter having an inflatable balloon at its distal end is introduced into the coronary artery, the uninflated balloon is positioned at the stenotic site, and the balloon is inflated. Inflation of the balloon disrupts and flattens the plaque against the arterial wall, and stretches the arterial wall, resulting in enlargement of the intraluminal passageway and increased blood flow. After such expansion, the balloon is deflated, and the balloon catheter removed.
Such a procedure is also used in arteries other than coronary arteries in the vascular system. In such a case, the procedure is referred to as percutaneous transluminal angioplasty (PTA) and is very similar to that described above for PCTA.
During PCTA or PTA, it is desirable to delivery a therapeutic agent or drug to area where the balloon angioplasty is occurring to prevent restenosis, repair vessel dissections or small aneurysms or provide other desired treatment.
Various drug delivery catheters have been developed that allow localized delivery of a therapeutic agent. In these catheters, typically a lumen is provided that allows the physician to deliver the drug to the balloon area of the catheter. There are, however, at least two drawbacks to this type of design. First, localized “jetting” of the drug from the lumen may damage the vessel. Second, there is a general difficulty or inability to control and maintain the drug in the desired treatment location.